The Maternal Health Practices and Child Development Project is a prospective epidemiologic study of the pregnancy outcome of 564 women who represent the entire spectrum of prenatal marijuana use. Women were interviewed in their fourth and seventh prenatal months and, with their offspring, assessed at delivery, 8 and 18 months and 3 and 6 years. This is a proposal to evaluate the children at age nine. The cohort was selected from an outpatient prenatal clinic and represents a general population sample of low income women, half of whom are white and half African-American. The assessment includes measures of sociodemographic status, the psychosocial environment of the mother and child, the household environment, current maternal substance use and the current substance use of the male in the household. At each phase, age-appropriate assessments of the developmental and physical status of the child are completed. Using cognitive, behavioral and biological measures, we have found that prenatal marijuana exposure can affect the central nervous system. It is important to evaluate the impact that this will have on the continued development of the children and to identify whether additional effects may be detected at older ages. We will measure cognitive development, neuropsychological functioning, psychological status, behavior and school achievement to determine the impact and the stability of the observed relationships between prenatal marijuana use and cognitive and psychosocial development. New assessments have been added to the protocol to measure these relationships in greater depth at an older age and to detect new effects that may occur as the children mature.